Field Guide To The Swan Point Sub-Reality Exclusion Zone is a FIST module similar in tone to Annihilation and Stalker.
The PDF is 6 pages, with dense text and only a few illustrations, but it's cleanly layed out and easy to read.
Contents-wise, Field Guide deals with an interdicted Massachusetts town that is experiencing some heavy dimensional otherness. A few locations in the town are written up, as are critters and related Traits.
The Traits fit perfectly into FIST, and shouldn't disrupt the balance of the core game at all. Similarly, the critters are flavorful but not overwhelming---each one presents an interesting tactical scenario without being unmanageable.
The writeup of the town is clever, and has some great eerie and surreal beats.
The supplement is also written as an in-universe document, which adds some nice flavor to the text throughout.
Overall, if you want a seed for a location-based FIST adventure, you should check this out. You'll need to do a little work in mapping out the town and figuring out a hook for the players, but most of that work is already done by the module itself.
Minor Issues:
-There's a reference to a Walmart in Swan Point, but those wouldn't have started to proliferate until the late 60s, and they spread from Arkansas.